The present invention is related to high temperature ceramic superconductor for use as a cryogenic current lead in a superconducting magnet.
In superconducting magnets current leads are used during ramp-up to energize the magnet. The leads can also be used during magnet operation to assure a constant current flowing through the winding in the presence of nonsuperconducting joints in the winding.
Cryogenic current leads are presently fabricated of helium cooled metallic resistive conductors, typically with high electrical and thermal conductivity. Helium cooling is required to reduce conduction heat transfer to the superconducting magnet and dissipate the resistance heating of the leads.
In many superconducting magnet systems where no loss of helium and refrigeration are essential to the economics of powering a magnet system cryogenic current leads must either be disconnected once magnet operation has been initiated or a reliquifier must be provided to reliquify the helium used in cooling the leads. Helium recondensors and cryocoolers and preferable to reliquifiers because they keep the helium contained in a closed loop system and have good reliability. A magnet cryostat equipped with a recondensor or cryocooler permits no loss of helium for vapor or liquid cooling and therefore thermal losses of conventional leads not cooled by helium cannot be tolerated for long.
It is an object of the present invention to provide a cryogenic current lead which does not require direct cooling with helium vapor.
It is a further object of the present invention to provide a cryogenic lead which provides a conduction heat transfer to the low temperature and comparable to that of conventional vapor cooled cryogenic leads.